Field of the Invention
The invention relates to a data line, in particular for use in a motor vehicle, and a method for producing such a data line.
Description of the Background Art
A data line may be formed as a coaxial cable is, for example, set out in U.S. Pat. No. 7,084,343 B1. The coaxial cable described therein comprises a central inner conductor, an insulation surrounding this as a dielectric, a multi-layered shielding as an outer conductor and an outer shell. The multi-layer shielding is thereby formed from a longitudinally folded shielding foil and a braided shield mounted above. With this structure, the coaxial cable is relatively stiff. As an alternative to the multi-layered shielding, this is designed in the form of a corrugated tube, as is known in so-called semi-rigid cables.
Due to the high rigidity, such a cable is of limited use in regions with alternating bending stresses. Also, because of the rigidity, its use in motor vehicles is often not practical.
Such a cable is also less suitable for use in the automotive industry for cost reasons, in particular because of the multi-layered shielding construction. In particular, the formation of the shielding constitutes one of the biggest cost and time factors. The shielding technically serves to keep radiation interference from the signals included inside the coaxial line and also to focus and guide a propagating field. For this purpose, the shielding is usually made of a braid, more rarely of a spiral shielding or a foil shielding. In a number of lines there are also combinations of different screen constructions. Braided shielding allows for only slow speeds to be realized during the manufacturing process, which results in a very large machine park of braiding machines, which inherently require a lot of staff, space and energy.
The semi-rigid cables are coaxial lines, wherein the outer conductors is formed of a closed tube. These cables have excellent electrical properties, however, are difficult to manufacture, expensive and almost inflexible.
Another coaxial cable is set out in U.S. Pat. No. 3,927,247. The shielding here is formed from a longitudinally folded shielding foil, which is in turn helically surrounded by ground wires. The shielding foil itself is designed of two or three layers with a plastic carrier film and a metal layer applied thereto. This shield structure is also relatively expensive to manufacture.
In addition to the coaxial lines, high-speed data lines are known in which normally one conductor pair is surrounded by a pair shielding. In these high-speed data lines, multilayered shielding foils are also habitually used for shielding. An example of such a data transmission cable with a wire pair surrounded by a pair shielding can be seen in DE 10 2008 019 968 A1. Here, the shielding foil is also folded longitudinally, wherein the one end of the film is additionally folded in an overlap region, so that a conductive layer is oriented to the outside towards a drain wire or ground wire, so that an electrical connection is formed to the grounding wire. Such high-speed data cables are used for very high transmission frequencies up into the gigahertz range. However, they are relatively expensive to manufacture.